Has this happened to you

I’m on birth control and I bleed every month during my placebo pills.

Last month I didn’t bleed at all. I took pregnancy tests and they were negative. I had my annual gynecologist appointment and they did a pregnancy test, and it was negative.

This month, I had some period cramps and extremely light bleeding. 🩸 very light pink.

This is very weird for me. I always bleed somewhat heavy for 3-4 days.

What do you think the cause could be ? It doesn’t seem like I’m pregnant?